Radio problems Options

[secra12]

Alright, under normal driving conditions, my radio is perfectly fine...however, when I get to about 5,000 RPMs, the radio will cut off until about 5.5-6000 RPMs, where it'll turn back on right before the car shifts. What would cause this?

The first time it happened, I was on my way to school and was trying to get onto a busy highway. On the on-ramp, I went to step on it and the car jerked a couple of times and the radio cut off. This happened about 3 weeks ago. My dad, who was a mechanic, thought it may have been the distributor going out, because the car developed a skip. Well, we replaced that and the problem still persisted-however, the car didn't jerk anymore and there wasn't a skip. Then he thought that the alternator might be going out, since it was a weaker 70amp...so I bought a 90amp replacement. After we installed it, the problem is STILL THERE! He doesn't know what it might be, but he insists that its the second battery in the trunk pushing too much voltage through the car. I think that the radio may be grounding out somewhere at the higher RPMs, as the radio grounded off somewhere else before and it blew the fuse under the hood (this was months ago, so I figured that it was just bad luck or something). We are both stumped.

I have a Kenwood Excelon radio wired to a 1500W Audiopipe Class D amp. The amp runs off a separate battery in the trunk, which also powers two 12" subwoofers. There are 8's for the door speakers in the front, with tweeters. For the rear speakers, there are Sony Explods. I haven't changed anything with this setup for months, and have no clue why this would just start happening. Can someone help me?!